Coronary and microvascular thrombolysis with guided diagnostic ultrasound and microbubbles in acute ST segment elevation myocardial infarction

Background: During a microbubble infusion, guided high-mechanical index impulses from a diagnostic two-dimensional transducer improve microvascular recanalization in acute ST-segment elevation myocardial infarction. The purpose of this study was to further elucidate the mechanism of improved microvascular flow in normal and hyperlipidemic atherosclerotic pigs. Methods: In 14 otherwise normal pigs, acute left anterior descending thrombotic coronary occlusions were created. Pigs subsequently received aspirin, heparin, and half-dose fibrinolytic agent (tenecteplase or tissue plasminogen activator), followed by randomization to either no additional treatment (group I) or a continuous infusion of nontargeted microbubbles and guided high-mechanical index impulses from a three-dimensional transducer (group II). Epicardial recanalization rates, ST-segment resolution, microsphere-derived myocardial blood flow, and ultimate infarct size using myocardial contrast echocardiography were compared. The same coronary thrombosis was created in a set of 12 hypercholesterolemic pigs, which were then treated with the same pharmacologic and ultrasound regimen (group III, n = 6) or the pharmacologic regimen alone (group IV, n = 6). Results: Epicardial recanalization rates in groups I and II were the same (29%), but peri-infarct myocardial blood flow and ultimate infarct size improved after treatment in group II (P <.01 vs group I). In group III, epicardial recanalization was 100% (vs. 50% in group IV), and there were significant reductions in ultimate infarct size (P =.02 compared with group IV). Conclusions: Guided high-mechanical index impulses from a diagnostic transducer and nontargeted microbubbles improve peri-infarct microvascular flow in acute ST-segment elevation myocardial infarction, even when epicardial recanalization does not occur.